Copeland Scroll Compressor Runs Backwards. If it is a three-phase scroll, determine the proper rotation at start up by observing that the suction pressure drops and discharge pressure rises. In addition, a phase monitor is recommended to eliminate the possibility of reverse rotation. Larger scrolls. Sep 5, 2005 - The only solution they offer is to check the blower motor and see what. The only sure way to verify the rotation on a scroll compressor is with a.
Good morning, everyone. I have been reading and searching on this site for a while (and props to everyone-there seems to be a whole lot of knowledge here) but this is my first time posting.I recently bought an Ingersoll Rand 2340-L5 air compressor. This is a 2-stage reciprocating compressor. It was sold to me for parts-I needed a new tank for my existing comp. And the shop that sold it to me said the compressor was knocking. They had just replaced the motor.
Well, I got it home and got looking at it, and I noticed the motor was wired for the wrong direction of rotation. It was spinning the pump backwards. So I corrected this and put the compressor back on the unit-and so far everything seems to be running fine, although I haven't put much time on it. Just ran it up to pressure and that's about it. This compressor is nicer (and much newer) than the one I have, so I'd like to use it if possible. So I'm wondering:1.What happens to a compressor like this when it's run backwards? I can't picture anything catastrophic happening, but since it was running backwards could it have made some strange noises and they decided the pump was bad?2.If I assume that the compressor WOULD run backwards, I could see having an issue of it not cooling properly since the flywheel was pulling air the opposite direction.
Is it more likely that it built up enough heat to cause the compressor to fail?Any other thoughts anyone has would be much appreciated.Thanks a lot,Tim Replies to this message: Air compressor knocking-running backwards?: - tf3891Posted by: randykimball ®, 09:17:18. I'm not sure about this, but it seems in my distant memory that there are some spiral oil grooves on some of the parts that move oil accordingly to rotation.
And I must make it clear here that the memory is really faded. If this is true, running it backwards will inhibit correct oiling of all parts. Plus such machines are generally designed with the compression side of the cycle to be on the correct side, only accomplished during correct rotation.
It also depends on the type of unloader installed, some may be rotation direction sensitive.As for knocking. I'd expect piston pin and journal slack. I've seen these things run for many many hours knocking. Keep it well oiled! When a compressor runs, we users tend to forget about them until they fail. If it by passes some oil you won't need as much oil for your air tools.
But the air is not healthy to breathe.A gravity chamber for oil and debri to be trapped into is a good idea. This would simply be a down line chamber with the air entering and leaving two ports near the top, having a drain at the bottom. The ports should be configured in such a way as to not allow the air to flow straight through. For example, have the inlet pointing straight down and the exhaust out one side near the top.The worst suggestion of your lifetime may be the catalyst to the grandest idea of the century, never let suggestions go unsaid nor fail to listen to them.Modified by randykimball at Thu, Jan 22, 2009, 00:22:08 :: Air compressor knocking-running backwards?: - randykimballPosted by: tf3891 ®, 12:35:49. So-when you say 'such machines are generally designed with the compression side of the cycle to be on the correct side' are you talking to the amount of advance of the crankshaft between the 1st and 2nd stages? ('amount of advance' is probably not the correct word, but I'm no engine designer) If thats the case, I can see how it might not function well.I think I will take your advice, plumb it right, and just keep an ear on it for now.
Overhaul kits for this pump are very expensive so I would like to catch the problem while it is small enough to repair- but at the same time the problem needs to be big enough to FIND, and I'm not hearing much. Not to mention it's pumping pretty well.Anyway, thanks again. Much appreciated. ::: Air compressor knocking-running backwards?: - tf3891Posted by: randykimball ®, 16:24:44. 'compression on the correct side'.
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When the crank is in compression stroke of a cylinder the load is down on the crank case bearings. When it is in the intake stroke the load is considerable less and on the top side of the bearings. Sometimes the crank case is actually designed for the crank shaft to be off center to better handle those long term load differences. Simplified, this allows the rod to be in a more vertical position (sort of) during peak torque load degrees.The worst suggestion of your lifetime may be the catalyst to the grandest idea of the century, never let suggestions go unsaid nor fail to listen to them.Modified by randykimball at Wed, Jan 21, 2009, 16:29:17 :::: Air compressor knocking-running backwards?: - randykimballPosted by: Kelly Bramble ®, 18:34:48.
I recently received the following question: Mike – have you posted a blog about the difference between recip and scroll compressors? We run into some resistance in some areas because we don’t use all scrolls. We try to answer this by stating that we design the compressor to fit the application, and that scrolls are not always the best fit. But you know contractors and if they think scrolls are better, we lose.Well, I have not posted anything on this subject and I know the factory answer is just what is stated above — that the compressor selection is based on best performance fit for the product. Most manufacturers can use either reciprocating or scroll compressors.
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It usually is not a matter of “space” since either will usually fit in the cabinet. I’m sure most manufacturers would love to have to stock only one type of compressor but, with the government changing efficiency requirements and manufacturers trying to keep up with those requirements, sometimes a recip gives the best efficiency and some times a scroll does.Now, as I have stated in the past, I am not an engineer so, as a “student of HVAC”, I started to research the subject. Believe it or not, PURDUE UNIVERSITY Department of Engineering actually did a study on the very subject. Below is a link to a paper they published and I have copied and pasted the conclusions they found from that paper.Over all, the scroll has some advantages but not in all cases which takes us back to why engineers use both types in equipment design. Keep in mind that engineers are designing to meet efficiency requirements. One of the disadvantages of scrolls is the higher power consumption by the scroll at overcharged condition. In fact, they found COP is reduced with significant under- and over-charging — and we all know that charge in today’s equipment is becoming more and more critical.
So if a tech is not taking their time, and is not accurate on their charge, the scroll could be less efficient than the recip.CONCLUSIONS: A series of steady state performance experiments were carried out using a scroll and a reciprocating compressor at two condenser operating conditions. The results show that the scroll compressor generally produces cooling capacities and COPs that are equal to or greater than the reciprocating compressor. The performance of the scroll compressor improves relative to the reciprocating compressor at the higher condenser temperature. The use of a liquid injection system allows the scroll compressor to produce lower discharge temperatures than the reciprocating compressor.A number of tests were also carried out to investigate the performance of both compressor types at varying charge levels. The scroll and reciprocating compressors show similar characteristics for cooling capacity and COP with respect to system charge level. The deterioration of the cooling capacity in the scroll is slower during overcharging than in the reciprocating but this is offset by the higher power consumption by the scroll at overcharged condition and so the COP variation is similar.
Generally, COP is slightly reduced with under-charging and significantly reduced with over-charging.The scroll and reciprocating compressors also show similar characteristics for superheat and subcooling with respect to charge level. For both compressor types, superheat decreases with increased charge level and subcooling increases significantly at charge levels above the nominal. The scroll compressor produces slightly greater superheat and considerably greater subcooling than the reciprocating compressor. The increase in subcooling for the scroll design is a result of the liquid injection system reducing the amount of de-superheating required in the condenser.The results suggest that scroll compressors may deliver performance advantages over reciprocating compressors at some operating conditions, particularly at higher condenser temperatures and this is because of the lower discharge temperature observed in the scroll. Both compressor types exhibit the same general characteristics with respect to system charge.
In particular, COP is reduced with significant under- and over-charging. Superheat and subcooling are shown to be functions of system charge level for both compressors and thus may be used as a general indicator of charge level, irrespective of the compressor type. (Taken from Purdue University. Purdue e-PubsGrace, I.; Datta, D.; and Tassou, S. A., ” Comparison Of Hermetic Scroll And Reciprocating Compressors Operating Under Varying Refrigerant Charge And Load ” (2002).
International Compressor Engineering Conference. About yorkcentraltechtalkI have been in the HVAC industry most of my life. I worked 25 years for contractors on anything from residential to large commercial boilers and power burners.
For the past 23+ years I had been employed by York International UPG Division ( a division of Johnson Controls) as a Technical support/Service Manager but I am now retired.One of my goals has always been to 'educate' dealers and contractors. The reason for starting this blog was to share some knowledge, thoughts, ideas, etc with anyone who takes the time to read it.The contents of this blog are my own opinions, thoughts, experiences and should not be construed as those of Johnson Controls York UPG in any way.I hope you find this a help. I always welcome comments and suggestions for postings and will do my best to address any thoughts, questions, or topics you may want to hear about.Thanks for taking the time to read my postings!Mike Bishop.